JP6065091B2 - Detection device, power reception device, power transmission device, non-contact power transmission system, and detection method - Google Patents

Description

  The present disclosure relates to a detection device, a power reception device, a power transmission device, a non-contact power transmission system, and a detection method that detect the presence of a conductor such as metal.

  In recent years, development of a non-contact power transmission system that supplies power (wireless power feeding) in a non-contact manner has been actively performed. There are roughly two types of methods for realizing wireless power feeding.

  One is an electromagnetic induction method that is already widely known. In the electromagnetic induction method, the degree of coupling between the power transmission side and the power reception side is very high, and high-efficiency power supply is possible. However, since it is necessary to keep the coupling coefficient between the power transmission side and the power reception side high, if there is a distance between the power transmission side and the power reception side or if there is a positional shift, the coil between the power transmission side and the power reception side The power transmission efficiency (hereinafter referred to as “coil efficiency”) is greatly deteriorated.

  The other is a method called a magnetic field resonance method, which has a feature that the magnetic flux shared between the power supply source and the power supply destination may be reduced by positively using the resonance phenomenon. In the magnetic resonance method, even if the coupling coefficient is small, the efficiency between coils does not deteriorate if the Q factor (Quality factor) is high. The Q value is an index representing the relationship between energy retention and loss (indicating the strength of resonance of the resonance circuit) of the circuit having the coil on the power transmission side or the power reception side. That is, there is a merit that the axis alignment of the power transmission side coil and the power reception side coil is unnecessary, and the degree of freedom of the position and distance between the power transmission side and the power reception side is high.

  One of the important elements in the non-contact power transmission system is a countermeasure against heat generation of metallic foreign matter. When power is supplied in a non-contact manner without being limited to the electromagnetic induction method or the magnetic field resonance method, an eddy current may be generated when a metal exists between the power transmission side and the power reception side, and the metal may generate heat. In order to suppress this heat generation, a number of methods for detecting metallic foreign objects have been proposed. For example, a method using an optical sensor or a temperature sensor is known. However, the detection method using a sensor is expensive when the power supply range is wide as in the magnetic field resonance method. For example, in the case of a temperature sensor, since the output result of the temperature sensor depends on the thermal conductivity of the surroundings, design restrictions are imposed on the devices on the transmission side and the reception side.

  Therefore, a method has been proposed in which the presence or absence of a metallic foreign object is determined by looking at changes in parameters (current, voltage, etc.) when a metallic foreign object enters between the power transmission side and the power receiving side. With such a method, it is not necessary to impose design restrictions and the like, and costs can be reduced. For example, Patent Document 1 discloses a method for detecting a metal foreign object based on the degree of modulation during communication between the power transmission side and the power receiving side, and Patent Document 2 discloses a method for detecting a metal foreign object based on eddy current loss (foreign object detection based on DC-DC efficiency). Proposed.

JP 2008-206231 A JP 2001-275280 A

  However, the methods proposed in Patent Documents 1 and 2 do not take into account the influence of the metal housing on the power receiving side. When charging a general mobile device, there is a high possibility that some metal (metal housing, metal parts, etc.) is used in the mobile device, and the change in parameters is "because of the influence of the metal housing" It is difficult to determine whether it is due to the contamination of metal foreign matter. Taking Patent Document 2 as an example, it is not known whether eddy current loss occurs in the metal housing of the portable device or whether metal alien substances are mixed between the power transmission side and the power reception side. Thus, it cannot be said that the methods proposed in Patent Documents 1 and 2 are capable of accurately detecting a metallic foreign object.

  The present disclosure has been made in consideration of the above-described situation, and improves the detection accuracy of the metallic foreign object existing between the power transmission side and the power reception side.

  One aspect of the present disclosure provides an AC signal for measurement at the time of Q value measurement in a state where power supply is stopped with respect to a resonance circuit including at least a coil and a capacitor included in a power transmission device or a power reception device constituting a non-contact power transmission system. Supply. Then, the Q value of the resonance circuit to which the AC signal for measurement is supplied is measured.

  According to one aspect of the present disclosure, an AC signal for measurement is supplied to the resonance circuit in a state where power feeding is stopped, and the Q value of the resonance circuit is measured.

  According to the present disclosure, the configuration of the resonance circuit at the time of power feeding and the configuration of the resonance circuit at the time of metal foreign object detection by Q value measurement are optimized to detect the metal foreign objects without impairing the power feeding performance. Accuracy can be improved.

It is a graph which shows the example of a relationship between the frequency and Q value in a coil. It is the graph which compared Q value for every frequency with the case where a metal foreign material mixes in a coil, and the case where it does not mix. It is a graph which shows the relationship between the frequency and the variation | change_quantity of Q value in the case where a metal foreign material is mixed, and the case where it does not mix. It is a circuit diagram which shows the outline | summary of the power transmission apparatus used for a non-contact electric power transmission system. It is a block diagram which shows the internal structural example of the power transmission apparatus (primary side) used for a non-contact electric power transmission system. It is a block diagram which shows the internal structural example of the battery-less power receiving apparatus (secondary side) used for a non-contact electric power transmission system. It is explanatory drawing of the concept of the partial pressure in the equivalent circuit supposing a series resonance circuit. FIG. 8 is a waveform diagram showing an example of a voltage signal observed at a designated point in the equivalent circuit shown in FIG. 7. A, B, and C are circuit diagrams showing configurations of different resonant circuits. It is a graph which shows the frequency characteristic of the impedance of the resonance circuit shown to FIG. 9A. It is a graph which shows the frequency characteristic of the impedance of the resonance circuit shown to FIG. 9B. It is a graph which shows the frequency characteristic of the impedance of the resonant circuit shown to FIG. 9C. It is explanatory drawing which shows the method of calculating the impedance value of a resonant circuit using a transfer function. It is an example of the graph which shows the relationship between a coupling coefficient and an impedance. A, B, and C are circuit diagrams showing connection examples of capacitors to coils of a resonance circuit. It is a block diagram showing an important section of an example of an internal configuration of a power receiving device (secondary side) according to the first exemplary embodiment of the present disclosure. It is a flowchart which shows the process at the time of the electric power feeding of the non-contact electric power transmission system based on 1st Example of this indication. It is a flowchart which shows the process in the case of performing Q value calculation reflecting a frequency sweep in the primary side (power transmission apparatus). It is an operation | movement timing chart in the non-contact electric power transmission system which concerns on the example of 1st Embodiment of this indication. It is a graph which shows an example of the relationship between the some frequency and Q value in a resonance circuit. It is a flowchart which shows the process in the case of performing Q value calculation in the primary side (power transmission apparatus). It is a block diagram which shows the principal part of the internal structural example of the power transmission apparatus (primary side) based on the 2nd Example of this indication. It is an equivalent circuit diagram which shows the structure of the resonance circuit when the 3rd switch of the power transmission apparatus (primary side) shown in FIG. 22 is turned on and turned off. It is a graph which shows the frequency characteristic of the impedance in a series resonance circuit. It is a graph which shows the frequency characteristic of the impedance in a parallel resonant circuit. FIG. 6 is a circuit diagram for calculating a Q value from a ratio of a real part component and an imaginary part component of impedance according to the third embodiment example of the present disclosure.

  Exemplary embodiments for carrying out the present disclosure will be described below with reference to the accompanying drawings. In addition, in this specification and drawings, about the component which has the substantially same function or structure, the overlapping description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The description will be made in the following order.
1. 1st Embodiment (Circuit switching part: The example which switched the electrostatic capacitance value of the capacitor at the time of electric power feeding and Q value measurement in the receiving side)
2. Second Embodiment (Circuit Switching Unit: Example of Switching Capacitance Value of Capacitor between Power Supply and Q Value Measurement on Power Transmission Side)
3. Others (Q factor measurement circuit: Modification of Q factor measurement process)

<1. First Embodiment>
[Introduction]
The metal foreign object detection technique in the present disclosure is a technique for detecting a metal foreign object using the above-described change in the Q value. The Q value is an index representing the relationship between energy retention and loss, and is generally used as a value representing the sharpness of resonance peak (resonance strength) of the resonance circuit. The metal foreign matter refers to a conductor such as a metal existing between the power transmission side (primary side) and the power reception side (secondary side), and the conductor includes a conductor in a broad sense, that is, a semiconductor.

  However, in this method, the resonance point (resonance frequency) needs to be adjusted at a certain Q value. Therefore, when power is supplied with an AC signal having a low Q value as in a general electromagnetic induction method, the absolute value of the Q value is low and the detection accuracy deteriorates.

FIG. 1 shows an example of the relationship between the frequency and the Q value in the coil.
The configuration of the coil used for the measurement is 8 turns with an outer diameter of 30 × 40 mm and an inner diameter of 20 × 30 mm. As shown in FIG. 1, the Q value indicated by the Q value frequency characteristic curve 1 varies greatly depending on the frequency. If this coil is used for power feeding at 100 kHz (resonance is caused by a capacitor), the absolute value of the Q value is about 50, and the Q value is about half or less compared to the maximum frequency.

FIG. 2 is a graph in which the Q value is compared for each frequency when the metal foreign matter is mixed into the coil and when it is not mixed.
In this example, the Q value is measured when a 15 mm square iron is placed in the center of the coil as a metal foreign object. It can be seen from FIG. 2 that the difference between the Q value frequency characteristic curve 2 when the metal foreign matter is mixed and the Q value frequency characteristic curve 1 when the metal foreign matter is not mixed increases as the frequency when the Q value is high.

FIG. 3 is a graph showing the relationship between the frequency and the amount of change in the Q value when a metallic foreign object is mixed and when it is not mixed. This shows the difference in the Q value for each frequency shown in FIG. 2 as a relative value.
It can be seen from FIG. 3 that the amount of change in the Q value varies greatly depending on the frequency, and from FIG. 2 and FIG. 3, the amount of change in the Q value increases as the absolute value of the Q value increases. That is, by detecting a metal foreign object using a frequency having a large absolute value of the Q value, the detection accuracy of the metal foreign object is improved.

[Principle of Q value measurement]
Here, the principle of Q value measurement will be described with reference to FIG.
FIG. 4 is a circuit diagram illustrating an outline of a power transmission device used in the non-contact power transmission system.
The circuit of the power transmission device 10 shown in FIG. 4 is an example of the most basic circuit configuration (in the case of magnetic field coupling) that represents the measurement principle of the Q value. Although a circuit including a series resonance circuit is shown, various configurations can be considered as long as the function of the resonance circuit is provided. This Q value measurement of the resonance circuit is a technique that is also used in a measuring instrument (LCR meter). In addition, although the example of the resonance circuit of the power transmission apparatus (primary side) was shown, this measurement principle can be similarly applied to the resonance circuit of the power reception apparatus (secondary side).

  If, for example, a metal piece is present as a metal foreign object near the primary coil 15 of the power transmission device 10, the magnetic lines of force pass through the metal piece and an eddy current is generated in the metal piece. From the viewpoint of the primary side coil 15, it appears that the metal piece and the primary side coil 15 are electromagnetically coupled and an actual resistance load is attached to the primary side coil 15. Change. By measuring the Q value, it is possible to detect a metal foreign object (electromagnetically coupled) near the primary coil 15.

  The power transmission apparatus 10 includes a signal source 11 including an AC power supply 12 and a resistance element 13 that generate an AC signal (sine wave), a capacitor (also referred to as a capacitor) 14, and a primary coil 15 (an example of a power transmission coil and a coil). Is provided. The resistance element 13 illustrates the internal resistance (output impedance) of the AC power supply 12. The capacitor 14 and the primary coil 15 are connected to the signal source 11 so as to form a series resonance circuit (an example of a resonance circuit). The capacitance value (C value) of the capacitor 14 and the inductance value (L value) of the primary coil 15 are adjusted so as to resonate at the frequency to be measured. The power transmission unit including the signal source 11 and the capacitor 14 transmits power to the outside through the primary coil 15 in a non-contact manner using a load modulation method or the like.

ｒ_ｓ：周波数ｆにおける実効抵抗値 When the voltage between the primary side coil 15 and the capacitor 14 constituting the series resonance circuit is V1 (an example of a voltage applied to the resonance circuit), and the voltage across the primary side coil 15 is V2, the Q value of the series resonance circuit is It is represented by Formula (1).

r _s : Effective resistance value at frequency f

The voltage V1 is multiplied by Q to obtain a voltage V2. When the metal piece approaches the primary coil 15 is effective resistance r _s increases, Q value decreases. When the metal piece approaches the primary side coil 15 in this way, the measured Q value (electromagnetically coupled state) changes. By detecting this change, the metal piece is close to the primary side coil 15. A metal piece can be detected.

[Configuration example of non-contact power transmission system]
(Configuration example of power transmission device)
FIG. 5 is a block diagram illustrating an internal configuration example of a power transmission device (primary side) used in the non-contact power transmission system.
The block diagram shown in FIG. 5 shows a more specific configuration of the power transmission device shown in FIG. 4, and a metal foreign object is detected by the Q value measurement circuit 20 (an example of a detection unit) shown in FIG. To do. The power transmission device provided with the Q value measurement circuit 20 is an example of a detection device.

  In this example, as examples of elements constituting the Q-value measuring circuit 20, rectifiers 21A and 21B, analog-digital converters (hereinafter referred to as “ADC”) 22A and 22B, and a main controller 23 are provided. . Each block constituting the power transmission device 10 including the block in the Q value measurement circuit 20 operates with electric power supplied from the signal source 11 or a battery (not shown).

  The rectifier 21A converts an AC signal (AC voltage) input from between the primary coil 15 and the capacitor 14 into a DC signal (DC voltage) and outputs the DC signal (DC voltage). Similarly, the rectifying unit 21B converts an AC signal (AC voltage) input from between the signal source 11 and the capacitor 5 into a DC signal (DC voltage). The converted DC signals are respectively input to ADCs 22A and 22B.

  Each of the ADCs 22 </ b> A and 22 </ b> B converts an analog DC signal input from the rectifying units 21 </ b> A and 21 </ b> B into a digital DC signal and outputs the digital DC signal to the main control unit 23.

  The main control unit 23 is an example of a control unit, and includes, for example, an MPU (Micro-Processing Unit) and controls the entire power transmission apparatus 10. The main control unit 23 has functions as an arithmetic processing unit 23A and a determination unit 23B.

  The arithmetic processing unit 23A is a block that performs predetermined arithmetic processing, and in this example, the ratio between the voltage V1 and the voltage V2, that is, the Q value is calculated from the DC signal input from the ADCs 22A and 22B, and the calculation result is determined. To the unit 23B. In addition, the arithmetic processing unit 23A may acquire information (physical quantity such as a voltage value) related to detection of a metal foreign object from the power receiving side (secondary side) and calculate the secondary side Q value based on the information. it can.

  The determination unit 23B compares the calculation result input from the arithmetic processing unit 23A with a threshold value stored in the nonvolatile memory 24, and determines whether or not a metal foreign object is nearby based on the comparison result. To do. The determination unit 23B can also compare the power reception side Q value with a threshold value to determine whether or not a metal foreign object is nearby.

  The memory 24 stores a threshold value (Ref_Q1) of a primary Q value measured in advance in a state where there is nothing in the vicinity of the secondary coil or nothing is placed in the secondary coil. The memory 24 also stores a threshold value (Q_Max) of the secondary Q value acquired from the power receiving side (secondary side).

  The communication control unit 25 is an example of a primary side communication unit, and performs communication with a communication control unit of a power receiving apparatus described later. For example, information related to detection of metallic foreign matter is transmitted and received, such as receiving the Q value of the resonance circuit including the secondary coil of the power receiving device, the voltage V1, the voltage V2, and the like. Further, the control of the main control unit 23 instructs the signal source 11 to generate and stop an AC voltage. As a communication standard in communication with the power receiving apparatus, for example, an IEEE 802.11 standard wireless LAN, Bluetooth (registered trademark), or the like can be used. In addition, it is good also as a structure which transmits information via the primary side coil 15 and the secondary side coil of a receiving device. In addition, an instruction may be issued directly from the main control unit 23 to the signal source 11 without going through the communication control unit 25.

  The input unit 26 generates an input signal corresponding to the user operation and outputs it to the main control unit 23.

  In this example, the power transmission device 10 has a built-in Q value measurement circuit 20 that can detect a metallic foreign object based on the primary Q value and detect a metallic foreign object based on the secondary Q value. Explains. Not only this but the power transmission apparatus 10 is provided with the main control part 23 which performs an arithmetic process and a determination process at least, and the communication control part 25, The function which determines an electromagnetic coupling state from the Q value of a power receiving apparatus, and detects a metal foreign material What is necessary is just to have.

  As described above, by applying the above measurement principle to the power receiving device (secondary side), the Q value can also be measured in the power receiving device. However, if power is supplied during the Q value measurement, a large electric power is generated in the coil of the power receiving device by the magnetic field emitted from the power transmission side, and the voltage V2 cannot be normally measured. Therefore, an accurate Q value cannot be obtained, and there is a possibility that a metal foreign object cannot be detected with high accuracy.

  In order to eliminate the above inconvenience, it is necessary to stop the power supply at the time of measurement. However, if the power supply is stopped, a large battery that operates a circuit for measuring the secondary Q value is indispensable. When a battery is loaded on the power receiving device, there is a negative effect on the product life, or a situation in which metal foreign object detection cannot be performed, for example, when it is desired to charge the battery immediately after the battery charge capacity of the portable device becomes empty.

  Therefore, the present inventors perform Q value measurement on the secondary side when receiving power from the primary side when performing Q value measurement on the secondary side using the power supplied from the primary side. We considered a battery-less electromagnetic coupling state detection technology that is not performed.

(Configuration example of power receiving device)
Hereinafter, a configuration example of a battery-less power receiving device (secondary side) used in the non-contact power transmission system will be described.
FIG. 6 is a block diagram illustrating an internal configuration example of a power receiving device applied to a mobile device or the like. The circuit is switched by switching between power supply and Q value measurement. At the time of Q value measurement, a metal foreign object is detected by a Q value measurement circuit 60 (an example of a detection unit). The power receiving device provided with the Q value measurement circuit 60 is an example of a detection device.

The power receiving device 30 of this example includes a secondary coil 31 and a capacitor 32 connected in parallel to the secondary coil 31, and one end of the secondary coil 31 and the capacitor 32 connected in parallel is one end of the capacitor 33. The other end of the capacitor 33 is connected to one input end of the rectifying unit 34. The other end of the secondary coil 31 and the capacitor 32 connected in parallel is connected to the other input terminal of the rectifier 34.
In addition, one output terminal of the rectifier 34 is connected to the input terminal of the first regulator 36 via the second switch 39, the output terminal of the first regulator 36 is connected to a load, and the other output terminal of the rectifier 34 is connected. Is connected to the ground terminal. A second regulator 37 is also connected to one output terminal of the rectifier 34.
Further, the capacitor 35 and the first switch 38 are connected in series, one end of the capacitor 35 is connected to one output terminal of the rectifier 34, and one end of the first switch 38 is connected to the other output terminal of the rectifier 34. ing.

  The first regulator 36 is controlled so as to always keep the output voltage and current constant, and as an example, supplies a voltage of 5 V to the load. Similarly, the second regulator 37 supplies a voltage of 3 V as an example to each block including each switch.

  A third switch 40 is connected to the other end of the capacitor 33, and is connected to an AC power supply 50 (oscillation circuit) via the third switch 40, the resistance element 52 and the amplifier 51. The input end of the amplifier 44 </ b> A is connected to the other end of the capacitor 33 via the third switch 41. On the other hand, the input end of the amplifier 44 </ b> B is connected to one end of the capacitor 33 via the third switch 42. Further, the secondary coil 31 and the other end of the capacitor 32 connected in parallel are connected to the ground terminal via the third switch 43.

  The first switch 38 (an example of the first switching unit), the second switch 39 (an example of the second switching unit), and the third switches 40 to 43 (an example of the third switching unit) have switching elements such as transistors and MOSFETs. Applied. In this example, a MOSFET is used.

  In this example, amplifiers 44A and 44B, subsequent envelope detectors 45A and 45B, and analog-digital converters (hereinafter referred to as “ADC”) 46A and 46B are examples of elements constituting the Q-value measuring circuit 60. And a main control unit 47 (arithmetic processing unit 47A, determination unit 47B).

  The output end of the amplifier 44A is connected to the envelope detector 45A. The envelope detector 45A detects the envelope of the AC signal (corresponding to the voltage V1) input from the other end of the capacitor 33 via the third switch 41 and the amplifier 44A, and supplies the detected signal to the ADC 46A.

  On the other hand, the output terminal of the amplifier 44B is connected to the envelope detector 45B. The envelope detector 45B detects an envelope of an AC signal (corresponding to the voltage V2) input from one end of the capacitor 33 via the third switch 42 and the amplifier 44B, and supplies the detected signal to the ADC 46B.

  Each of the ADCs 46 </ b> A and 46 </ b> B converts the analog detection signal input from the envelope detection units 45 </ b> A and 45 </ b> B into a digital detection signal and outputs the digital detection signal to the main control unit 47.

  The main control unit 47 is an example of a control unit, and includes, for example, an MPU (Micro-Processing Unit) and controls the entire power receiving device 30. The main control unit 47 has functions as an arithmetic processing unit 47A and a determination unit 47B. The main control unit 47 supplies the drive signal to each switch (the gate terminal of the MOSFET) using the power supplied from the second regulator 37 to control on / off (switch switching function).

  The arithmetic processing unit 47A is a block that performs predetermined arithmetic processing, calculates the ratio between the voltage V1 and the voltage V2, that is, the Q value from the detection signals input from the ADCs 46A and 46B, and outputs the calculation result to the determination unit 47B. To do. In addition, the arithmetic processing unit 47A can transmit information (voltage value and the like) of the input detection signal to the power transmission side (primary side) according to the setting. In addition, a frequency sweep process is performed during the metal foreign object detection process (sweep process function).

  The determination unit 47B compares the Q value input from the arithmetic processing unit 47A with a threshold value stored in the nonvolatile memory 48, and determines whether or not a metal foreign object is nearby based on the comparison result. . As will be described later, it is also possible to transmit the measured information to the power transmission device 10, and to calculate the secondary side Q value and determine the presence or absence of metal foreign matter in the power transmission device 10.

  The memory 48 stores a threshold value to be compared with the Q value measured in advance in a state where nothing is present in the vicinity of the secondary coil 31 or nothing is placed on the secondary coil 31.

  The communication control unit 49 is an example of a secondary side communication unit, and performs communication with the communication control unit 25 of the power transmission device 10. For example, the transmission / reception of information related to the detection of a metallic foreign object is performed such as transmitting the Q value of the resonance circuit including the secondary coil 31 of the power receiving device 30, the voltage V1, the voltage V2, and the like. The communication standard applied to the communication control unit 49 is the same as the communication standard applied to the communication control unit 25 of the power transmission device 10. In addition, it is good also as a structure which transmits information via the secondary side coil 31 and the primary side coil 15 of the power transmission apparatus 10. FIG.

  The AC power supply 50 generates an AC voltage (sinusoidal wave) when measuring the Q value based on the control signal of the main control unit 47 and supplies the AC voltage (sine wave) to the other end of the capacitor 33 via the amplifier 51 and the resistance element 52.

  The input unit 53 generates an input signal corresponding to the user operation and outputs it to the main control unit 47.

  The Q value measurement circuit 60 of the power receiving device 30 configured as described above is controlled by switching on / off of three switch groups, that is, the first switch 38, the second switch 39, and the third switches 40 to 43. Is done. Hereinafter, the operation of the power receiving device 30 will be described with attention paid to switching of each switch.

First, the power received from the power transmission device 10 by the secondary coil 31 is charged in a capacitor 35 (an example of a power storage unit) provided at the subsequent stage of the rectifying unit 34. The current value and time that can be operated with the power charged in the capacitor are determined by CV = it.
Here, C is the capacitance of the capacitor, V is the voltage value of the capacitor, i is the current value of the capacitor, and t is time. That is, when the voltage value charged in the 10 μF capacitor changes from 9 V to 4 V, for example, a current of 50 mA can flow for 1 msec. If the capacitance value of the capacitor is large, it is possible to apply a larger current or to extend the time for supplying the current.

  However, if a capacitor 35 having a large capacitance value is inserted in the subsequent stage of the rectifying unit 34, a malfunction may occur during communication between the power receiving device 30 and an external device. Is desirable. In other words, the drain-source of the first switch 38 is conducted only when measuring the Q value, and the adverse effect is eliminated by connecting the capacitor 35.

  If the consumption current of the Q value measuring circuit 60 is small to some extent and the time for measuring the Q value is short, it is possible to measure the Q value while stopping the carrier signal from the power transmission device 10. When stopping the carrier signal output from the power transmission device 10 (when measuring the Q value), it is necessary to reliably disconnect the load from the Q value measurement circuit 60. For example, a P-channel MOSFET may be used for the second switch 39, and control may be performed using a control that turns off when a carrier signal is input to the power receiving device 30, or an enable function of the first regulator 36. When other capacitors 35 are charged or when communication is performed through the communication control unit 49, there is no problem even if the load is not disconnected from the Q value measurement circuit 60.

  When measuring the Q value, the voltage value across the capacitor 33 is measured in the same manner as the measuring instrument (LCR meter) described above. Specifically, the third switches 40 to 43 are turned on at the timing when the carrier signal is stopped, and Q is determined from two voltage waveforms detected at one end and the other end of the capacitor 33 rectified from the sine wave output from the AC power supply 50. Calculate the value. Metal foreign matter is detected by comparing the calculated Q value with a preset threshold value.

[Deterioration of signal to noise ratio during Q factor measurement]
Incidentally, the accuracy of Q value measurement is greatly influenced by the impedance value at the resonance point (resonance frequency) of the resonance circuit. As described above, in the configuration of the power receiving device 30 illustrated in FIG. 6, the circuit at the time of power supply and the measurement of the Q value are switched by switching. That is, the voltage across the capacitor 33 is divided by the on-resistance of the third switch 41 and the impedance at the resonance point of the secondary coil 31, and the voltage amplitude is reduced. Therefore, depending on the impedance at the resonance point of the secondary coil 31, the voltage division ratio increases, and the SN ratio at the time of Q value measurement may be deteriorated.

FIG. 7 shows the concept of voltage division in an equivalent circuit assuming a series resonant circuit. FIG. 8 shows the result of trial calculation of the voltage waveform at each point of the equivalent circuit of FIG.
In FIG. 7, Z1 represented by a broken line represents the on-resistance (on-resistance component R1) of the switching element. Further, Z2 indicated by a broken line indicates a series resonance circuit, and an equalization circuit including an effective resistance component (effective resistance component r1) at the frequency f of the AC voltage of the coil L1, the capacitor C1, and the AC power source E. .

In the series resonance circuit, since the impedance at the resonance point is only the pure resistance of the coil L1, the voltage is divided at the point V1-1 and the point V1-2 (corresponding to V1 in FIG. 6) shown in FIG. The amplitude of the voltage becomes small.
The result of actually calculating the amplitude of the alternating voltage at the point of V1-1 and the point of V1-2 by simulation is the waveform diagram shown in FIG. The various conditions used for the trial calculation are: the frequency of the alternating voltage is 90 kHz, the amplitude is 0.1 V, the self-inductance of the coil L1 of the series resonance circuit is 14.3 μH, the resistance value of the effective resistance component r1 is 0.6Ω, and the capacitor C1 The capacitance value is 227 nF, and the resistance value of the on-resistance component R1 is 3Ω.
In FIG. 8, the waveform with a large amplitude indicates the level at the point of V1-1, and the waveform with a small amplitude indicates the level at the point of V1-2. From this voltage waveform, it can be seen that the amplitude of the AC voltage is certainly small.

Next, it will be described that the impedance at the resonance point of the resonance circuit varies depending on the configuration of the resonance circuit.
9A, 9B, and 9C are circuit diagrams showing configurations of different resonant circuits.
The resonant circuit of FIG. 9A is a series resonant circuit. On the other hand, the resonant circuits of FIGS. 9B and 9C each include a capacitor C1 ′ or C1 ″ connected in series with the coil L1, and a capacitor C2 ′ or C2 ″ connected in parallel with the coil L1.

  9A to 9C, as in the case of FIG. 8, the frequency of the AC voltage is 90 kHz, the amplitude is 0.1 V, the self-inductance of the coil L1 is 14.3 μH, and the resistance value of the effective resistance component r1 is 0. .6Ω, and the resistance value of the on-resistance component R1 is 3Ω. However, the capacitance value of the capacitor C1 in FIG. 9A is 227 nF, the capacitance values of the capacitors C1 ′ and C2 ′ in FIG. 9B are 168 nF and 59 nF, respectively, and the capacitances of the capacitors C1 ″ and C2 ″ in FIG. The values are 113 nF and 113 nF, respectively.

FIG. 10 is a graph showing the frequency characteristics of the impedance of the resonance circuit shown in FIG. 9A.
FIG. 11 is a graph showing the frequency characteristics of the impedance of the resonance circuit shown in FIG. 9B.
FIG. 12 is a graph showing frequency characteristics of impedance of the resonance circuit shown in FIG. 9C.
10 to 12, it can be seen that the impedance value of the resonance circuit differs depending on the constant of the resonance circuit even though the resonance frequency (90 kHz in this example) is the same. 10 is about 0.6Ω, FIG. 11 is about 1.1Ω, and FIG. 12 is about 2.4Ω. The larger the capacitance value of the capacitor connected in parallel to the coil L1, the larger the impedance value at the resonance point. ing.

  FIG. 13 is a circuit diagram illustrating a method for calculating the impedance value of the resonance circuit using a transfer function by a computer. The circuit example shown in FIG. 13 has the same circuit configuration as the equivalent circuit of the resonance circuit shown in FIGS. 9A and 9B.

となる。 From FIG. 13, the impedance from Z1 to Z3 indicated by the broken line is

It becomes.

なので、

となる。 Here, Z4 is

So,

It becomes.

となり、これを簡単化すると、

となる。 Therefore, the overall impedance Z5 is Z5 = Z1 + Z4.

And to simplify this,

It becomes.

  By obtaining the impedance at the point (resonance point) where the imaginary part becomes 0 from the equation (8), the simulation result of the resonance circuit of FIG. 13 can be obtained.

  However, when the capacitance value of the capacitor connected in parallel to the coil of the resonance circuit increases during power supply, the impedance value on the secondary side during power supply increases, and the voltage applied to both ends of the secondary load increases. There is a problem of end.

The optimum impedance value for the efficiency between the primary side coil and the secondary side coil during power feeding is determined by the self-inductance, Q value, coupling coefficient, etc. of the coil. As an example, FIG. 14 shows an example of the relationship between the coupling coefficient and the impedance.
In consideration of the above, when the coil size and the distance between the primary and secondary coils are determined to some extent and the target impedance value on the secondary side is also determined, the capacitor connection form, that is, the configuration and constants of the resonance circuit are also determined. It will be decided automatically.

15A, 15B, and 15C are circuit diagrams illustrating examples of connection forms of capacitors with respect to the coils of the resonance circuit.
The connection form of the capacitor to the coil of the resonance circuit is
(1) Series connection to the coil (FIG. 15A),
(2) Parallel connection to the coil followed by series connection (FIG. 15B),
(3) Parallel connection to the coil (FIG. 15C)
There are three types, and in some cases, any circuit configuration can be used.

The impedance at the resonance point at the time of Q value detection is the same value as when the coupling coefficient of the graph shown in FIG. 12 is 0, the minimum value in the above (1), the maximum value in the above (3). In the case of (2) above, the value is between them.
Therefore, there is a problem that the optimum configuration of the resonance circuit at the time of power feeding does not necessarily match the optimum configuration of the resonance circuit at the time of Q value measurement.

[Configuration Example According to First Embodiment]
(Configuration example of capacitor and switch)
Therefore, a method for switching the configuration (constant) of the resonance circuit between power feeding and foreign object detection by Q value measurement is proposed.

FIG. 16 illustrates a main part of an internal configuration example of a power receiving device (secondary side) that switches the configuration (constant) of a resonance circuit between power feeding and Q value measurement according to the first embodiment example of the present disclosure. FIG.
Compared with the power receiving device 30 shown in FIG. 6, the power receiving device 30 </ b> A according to the present embodiment includes a capacitor 32 ′ and a capacitor 33 ′ added to the resonance circuit, and a third switch 43 ′. The other is the same. Note that the third switches 40 to 43, 43 'are in an off state during power feeding and appear to be open, so there is no fear of adverse effects during power feeding.

  The capacitor 32 ′ is connected in parallel with the capacitor 32. The capacitor 33 ′ is connected in series with the capacitor 33 when the third switches 40 and 41 are turned on. The third switch 43 ′ to which a transistor, a MOSFET, or the like is applied is connected between the capacitor 32 ′ and the ground terminal. The third switches 41 and 43 ′ are an example of a circuit switching unit.

The switches of the third switch are turned on at the same time when the Q value is measured. The capacitor 32 ′ is in parallel with the capacitor 32, and the capacitance value of the capacitor in parallel with the secondary coil 31 is increased by turning on the third switch 43 when measuring the Q value, and at the resonance point of the resonance circuit. It plays a role to raise the impedance of the. As described above, by increasing the impedance at the resonance point, it is possible to keep the amplitude level of the AC voltage detected at the time of Q value measurement high, leading to an improvement in the SN ratio.
Note that the capacitor 32 may or may not be provided (a series resonant circuit may be used when power is supplied).

The capacitor 33 ′ is connected in series with the capacitor 33, and has a role of reducing the capacitance value of the capacitor connected in series with the secondary coil 31 during power feeding. By reducing the capacitance value of the capacitor in series with the secondary coil 31 during the Q value measurement, the frequency at the resonance point can be increased.
Thereby, it is also possible to return the resonance frequency that has been lowered by increasing the capacitance value of the capacitor in parallel with the secondary coil 31 during the Q value measurement. Furthermore, as described above, when the Q value is a low frequency at the time of power feeding, it is possible to increase the frequency at the time of Q value measurement.

  The configuration of the Q value measuring circuit 60 shown in FIG. 6 can be used for the Q value measuring circuit of the power receiving device 30A. The Q-value measuring circuit 60 measures the voltage at both ends of the capacitors 33 and 33 ′ connected in series, that is, the voltage at the point V 1 ′ (voltage V 1 ′) and the voltage at the point V 2 (voltage V 2). .

In this way, by appropriately switching the third switches 40 to 43, 43 ′, the measurement signal (sine wave signal) output from the secondary AC power source used for the Q value measurement and the power supply from the primary side are supplied. Thus, it is possible to calculate the Q value with high accuracy by preventing interference with the supplied power signal.
In addition, the configuration of the resonance circuit at the time of power feeding and the configuration of the resonance circuit at the time of metal foreign object detection by Q-factor measurement are each optimized (constant: capacitance value), thereby deteriorating the power feeding performance. Therefore, it is possible to improve the detection accuracy of the metallic foreign matter.
Even when power is not supplied from the power transmission side to the power reception side, metal foreign objects existing between the power transmission side and the power reception side are detected, and the configuration of the resonance circuit is switched when metal foreign objects are detected by Q-value measurement. Improve detection accuracy. Therefore, when detecting a metallic foreign object by Q-factor measurement, a frequency different from that at the time of power feeding is selected and supplied to the resonance circuit, which depends on the coil diameter and the wireless power feeding method (magnitude of coupling coefficient) such as electromagnetic induction method or magnetic field resonance method. Therefore, it is possible to detect a metallic foreign object by Q value measurement.

  In the example of FIG. 16, the case where the resonance frequency is raised by switching the circuit configuration of the resonance circuit when shifting from power supply to Q value measurement is described, but as understood from FIGS. 1 to 3, When the resonance frequency is high, the Q value may be measured by reducing the frequency to a frequency that maximizes the Q value.

  In the example of FIG. 16, a case is described in which the value of capacitance (capacitance component) in parallel and in series with the coil of the resonance circuit is changed when shifting from power feeding to Q value measurement. However, only the capacitance in parallel with the coil may be changed (increased as an example) or only the capacitance in series with the coil may be changed (decreased as an example). In order to change the capacitance, the capacitance may be changed by switching the capacitor to another capacitor.

In the present embodiment, the connection form of the capacitor to the coil of the resonance circuit is
(1) Series connection to coil (2) Parallel connection to coil and series connection (3) Applicable to any case of parallel connection to coil.
Note that when the capacitor of the resonance circuit when not measuring the Q value is only connected in parallel to the coil (3), for example, there is no capacitor 33 with respect to the secondary coil 31 of FIG. When only the third switch is turned on, only the capacitor 33 'is connected in series with respect to the parallel connection of the secondary coil 31 of the resonance circuit and the capacitor when the third switch is turned on.

[Overall control of non-contact power transmission system]
Here, the overall control process of the non-contact power transmission system according to the first embodiment of the present disclosure will be described.

FIG. 17 is a flowchart illustrating processing at the time of power feeding in the non-contact power transmission system configured to include the power transmission device 10 (see FIG. 5) and the power reception device 30A (see FIG. 16).
First, when the power transmission device 10 (primary side) is activated and the power reception device 30A (secondary side) is placed near the power transmission device 10, negotiation is performed between the power transmission device 10 and the power reception device 30A. After the power transmission device 10 and the power reception device 30A recognize each other, power supply is started. The power transmission device 10 or the power receiving device 30A performs Q value measurement at the start of power supply, and determines whether or not the number of times of Q value measurement is the first time (step S1).

  As an example, if the power of the power transmitting device 10 or the power receiving device 30A is immediately turned on, each device determines that it is the first Q value measurement. Alternatively, as a result of the negotiation, the power transmission device 10 determines from the ID information (identification information) of the power reception device 30A that the power reception device 30A is the first communication partner and is the first Q value measurement. Alternatively, the power transmission device 10 may receive the result of the number of Q value measurements calculated by the power receiving device 30A from the power receiving device 30A during the negotiation to grasp the number of Q value measurements.

As yet another example, the determination may be made based on the elapsed time from the previous Q value measurement. The power transmission device 10 (and the power receiving device 30A) has a clock unit (not shown), and stores the measured Q value in the memory 24 (and the memory 48) in association with the measurement time when the Q value is measured.
Then, the previous Q value measurement time is compared with the current Q value measurement time, and if there is a time difference exceeding a predetermined value, it is determined that the first Q value measurement is performed. The number of times of Q value measurement is, for example, the first time is Q value measurement with frequency sweep, and the number of times is calculated based on this. Note that the timer function of the clock unit may be activated during the previous Q value measurement, and the determination may be made based on the elapsed time of the timer.

  In the case of the first Q value measurement, the power receiving device 30A uses a plurality of frequencies (sweep measurement) for the measurement test signal (sine wave) output from the AC power supply 50, and obtains a plurality of secondary results. The largest Q value is obtained from the side Q values (step S2). The frequency of the test signal when the Q value is the largest is stored in the memory 48. Details of the processing in step S2 will be described later.

  In order to measure the Q value, it is necessary to input a sine wave having a resonance frequency to the power receiving device 30A. However, resonance also occurs due to variations in the component quality of the power receiving device 30A, variations in the positional relationship between the coil and the metal in the device (for example, the housing) at the time of mounting, the environment around the secondary side coil 31, and contamination of metallic foreign matter. The frequency changes. Therefore, it is necessary to search for the resonance frequency by taking into account the deviation of the resonance frequency and performing measurement (frequency sweep) using a plurality of different frequencies within a certain appropriate range (measurement range).

  This frequency sweep is always necessary for the first Q-factor measurement in consideration of the entire non-contact power transmission system, but can be omitted after the second time. As an example in which the frequency sweep can be omitted in the second and subsequent Q-value measurements, there is a case where the positional relationship between the power transmission device 10 and the power receiving device 30A has not changed significantly from the initial Q-value measurement.

  On the other hand, if it is not the first Q value measurement in the determination process of step S1, power receiving apparatus 30A obtains a Q value by using a test signal having a frequency obtained by the first Q value measurement (step S3). Details of the processing in step S3 will be described later.

  The power transmitting device 10 or the power receiving device 30A determines whether or not there is a possibility that a metallic foreign object exists based on the secondary side Q value (step S4). If there is no possibility that there is a metallic foreign object, the process proceeds to step S6.

  On the other hand, if there is a possibility that a metallic foreign object is present in the determination process of step S4, the process proceeds to step S2, and the power receiving apparatus 30A performs a frequency sweep of the test signal, and the largest Q of the plurality of secondary side Q values is obtained. Get the value.

  After the process of step S2 is complete | finished, the power transmission apparatus 10 or the receiving device 30A determines the presence or absence of a metal foreign material based on the secondary side Q value obtained by calculation (step S5). When there is a metallic foreign object, the power supply is forcibly terminated or a warning is given to the user as a termination process. As the power supply compulsory termination processing, there is a method in which the power transmission device 10 stops power transmission, or even if the power transmission device performs power transmission, the power reception device 30A stops power reception.

  The Q value measurement in steps S2 to S5 described above is performed using the power charged in the power storage unit (capacitor 35). For example, in the case of frequency sweep, after charging the capacitor 35 with a charge sufficient to measure the Q value (that is, the voltages V1 ′ and V2) for a test signal of one frequency, the Q value is measured, charged again, and the next frequency Repeat the measurement of the Q value for the test signal.

  If there is no metal foreign object in step S5, power is supplied from the power transmission device 10 to the power reception device 30A for a predetermined time (step S6).

  Finally, the power receiving device 30A determines whether or not a battery (load) (not shown) is fully charged, and communicates the result to the power transmitting device 10 (step S7). If the battery is fully charged, the charging process is terminated. If the battery is not fully charged, the process proceeds to step S1 and the above process is repeated. Note that the determination of whether or not the battery is fully charged and communication may be performed during power feeding.

  In this way, the frequency sweep is performed only for the first Q value measurement, and the Q value measurement is performed only for the test signal having the frequency optimized for the first time after the second time. However, when it is determined that there is a possibility that a metallic foreign object exists after the second time, there is a possibility of frequency shift due to a change in the positional relationship between the primary side coil and the secondary side coil. Make a decision by sweeping the frequency. If it is determined that there is a metal foreign object even after sweeping the frequency, the power supply is forcibly terminated or a warning is given to the user. This method can significantly reduce the time for Q value measurement.

[Example of Q value calculation with frequency sweep on the primary side]
Next, the process in the case of performing Q value calculation with frequency sweep in step S2 on the primary side will be described.
Since the frequency sweep is performed, it is assumed that it is determined to be the first Q value measurement. This processing may be performed when the power transmission device 10 determines that it is the first Q value measurement, or when the power receiving device 30A determines that it is the first Q value measurement and transmits the result to the power transmission device 10. .

FIG. 18 is a flowchart illustrating a process when a Q value calculation reflecting a frequency sweep is performed on the primary side (power transmission device 10).
First, after the negotiation with the main control unit 47 of the power receiving device 30A is completed, the main control unit 23 of the power transmission device 10 outputs an electromagnetic wave from the primary coil 15 to transmit power to the power receiving device 30A (transmission of a carrier signal). ) Is started (step S11). The main control unit 47 of the power receiving device 30A receives the electromagnetic wave output from the power transmitting device 10 from the secondary coil 31 and starts a power receiving process (step S12).

  When the power transmission process is started, the main control unit 23 of the power transmission device 10 transmits the first Q value measurement command to the power receiving device 30A through the communication control unit 25 (step S13). The main control unit 47 of the power receiving device 30A receives the first Q value measurement command from the power transmission device 10 through the communication control unit 49 (step S14).

FIG. 19 is an operation timing chart in the non-contact power transmission system according to the first embodiment example of the present disclosure.
In the present embodiment, a “Q value measurement period (61-1, 61-2, 61-3)” for performing Q value measurement processing and a “Q value measurement period” for performing processing such as power supply (other than Q value measurement). “Power supply periods (62)” are alternately set. When communication between the power transmission device 10 and the power reception device 30A is established, the main control unit 23 of the power transmission device 10 issues the first Q value measurement command in step S13. As an example, the first Q-value measurement command is transmitted at the head of the first Q-value measurement period 61-1. The first Q value measurement period is “Charge”, “Q value measurement at frequency f ₁ ”, “Charge”, “Q value measurement at frequency f ₂ ”,..., “Q value at frequency f _n−1 It is divided into a plurality of periods of “measurement”, “charge”, “Q value measurement at frequency f _n ”, “charge”, and “communication to primary side”.

The main control unit 47 of the power receiving device 30A switches on / off of the first switch 38, the second switch 39, and the third switches 40 to 43, 43 ′ corresponding to the plurality of periods. The following is the main switching timing of the first switch 38, the second switch 39, and the third switches 40 to 43, 43 ′.
1) The first switch 38 is turned on during the Q value measurement period (charging the capacitor 35), and is turned off during other periods (power supply period).
2) The second switch 39 is turned off during the Q value measurement period, and is turned on during other periods (power supply period).
3) The third switches 40 to 43, 43 ′ are turned on during the Q value measurement period (particularly when the voltages V1 ′, V2 are detected), and are turned off during other periods.

  When receiving the first Q value measurement command, the main control unit 47 of the power receiving device 30A turns on the first switch 38, electrically connects the rectifying unit 34 and the capacitor 35, and receives the power received from the primary side. Charge. At this time, the second switch 39 is turned off, and the first regulator 36, that is, the load is disconnected from the capacitor 35 (step S15).

Subsequently, the AC power supply 50 of the power receiving device 30 </ b> A outputs a test signal (sine wave) for measurement under the control of the main control unit 47. The frequency Freq of the test signal at this time is set to an initial value (f ₁ ) (step S16).

  The main control unit 23 of the power transmission device 10 stops power transmission (carrier signal transmission) to the power reception device 30A (step S17). The waiting time from the start of power transmission in step S13 to the stop of power transmission in step S17 is equal to or longer than the time required for at least the capacitor 35 to be charged with the required power (power required for Q value measurement at one frequency). It is.

  The main control unit 47 of the power reception device 30A stops power reception when power transmission from the power transmission device 10 is stopped (step S18).

Here, the main control unit 47 turns on the third switches 40 to 43, 43 ′ (step S19). When the third switch 40 is turned on, the test signal having the frequency f ₁ generated by the AC power supply 50 is supplied to the other end of the capacitor 33 ′ through the third switch 40. Further, the third switch 41 is turned on to conduct the other end of the capacitor 33 'and the input terminal of the amplifier 44A, and the third switch 42 is turned on to conduct one end of the capacitor 33 and the input terminal of the amplifier 44B.

  The main control unit 47 detects the voltage V1 ′ at the other end of the capacitor 33 ′ by the amplifier 44A, the envelope detection unit 45A, and the ADC 46A, and records it in the memory 48. Similarly, the voltage V2 at one end of the capacitor 33 is detected by the amplifier 44B, the envelope detector 45B, and the ADC 46B and recorded in the memory 48 (step S20).

After the frequency of the test signal has been acquired voltage V1 ', V2 when the _{f 1,} the main control unit 47 turns off the third switch 40～43,43' (step S21).

  Here, the main control unit 23 of the power transmission device 10 starts power transmission to the power receiving device 30A again (step S22). The waiting time from the stop of power transmission in step S17 to the start of power transmission in step S22 is at least equal to or longer than the time required to detect and record the voltages V1 ′ and V2. Then, after restarting power transmission to the power receiving device 30A in step S22, the main control unit 23 of the power transmission device 10 proceeds to step S17 after the waiting time for charging the capacitor 35 has elapsed, and stops power transmission again. The waiting time from the start of power transmission in step S22 to the stop of power transmission in step S17 is at least equal to or longer than the time required to charge the capacitor 35 with the required power.

The main control unit 47 of the power receiving device 30A starts receiving power from the power transmitting device 10 in response to the restart of power transmission of the power transmitting device 10, and charges the capacitor 35 (step S23). During the waiting time for charging the capacitor 35, the AC power supply 50 of the power receiving device 30A outputs a test signal of the next frequency Freq according to the control of the main control unit 47 (step S24). The frequency Freq of the test signal at this time is _{f 2.}

The main control unit 47 of the power receiving device 30A proceeds to step S18 after the waiting time for charging the capacitor 35 has elapsed after the processing of step S24 is completed, and stops power reception when power transmission from the power transmitting device 10 is stopped. To do. Then, step S19 continues the subsequent processing, performed Q value measured at the test signal frequency _{f 2,} to obtain the voltage V1 ', V2.

  In the period from the stop of power reception in step S18 to the start of power reception in step S23 (steps S19 to S21), each block of the detection circuit operates only with the electric power charged in the capacitor 35.

  The main control unit 47 of the power receiving device 30A turns off the first switch 38 and disconnects the capacitor 35 from the detection circuit when the processing (frequency sweep) for acquiring the voltages V1 ′ and V2 for each of the test signals having a plurality of frequencies is completed. (Step S25). Subsequently, the main control unit 47 of the power receiving device 30A controls the AC power supply 50 to stop the output of the test signal (step S26).

  Then, the main control unit 47 of the power receiving device 30A makes a response to the first Q value measurement command from the power transmitting device 10. As a response, the threshold value used for the determination of the metallic foreign object stored in the memory 48 and the measurement data group (Freq, V1, V2) obtained using the test signals of a plurality of frequencies are transmitted through the communication control unit 49. (Step S27).

  In the flowchart shown in FIG. 18, the second switch 39 is turned off while the capacitor 35 is being charged, and the first regulator 36 (load) is disconnected from the capacitor 35 (see step S15). However, the capacitor 35 is being charged. Alternatively, power may be supplied to the load. The power supply (charging to the capacitor 35) may be stopped at least during the Q value measurement (particularly when the voltages V1 ′ and V2 are detected), and the power supply is continued while the communication and the capacitor 35 are charged. Or may be stopped. The same applies to the flowchart of FIG. 21 described below.

  After the process of step S27, the power transmitting apparatus 10 receives the threshold value and the measurement data group (Freq, V1 ′, V2) from the power receiving apparatus 30A and stores them in the memory 24 (step S28).

Then, the arithmetic processing unit 23A of the power transmission device 10 calculates the secondary-side Q value from the voltages V1 ′ and V2 for each frequency Freq of the test signal received from the power reception device 30A based on the formula (1). And a Q value table are created and stored in the memory 24. When the relationship between the frequency of the test signal and the Q value is graphed, it can be expressed as shown in FIG. The largest secondary-side Q value (Q_Max) is determined (step S29). In the example of FIG. 11, the Q value at the frequency f ₀ in the vicinity of the maximum value of the frequency characteristic curve of the Q value is Q_Max.

  Next, the determination unit 23B of the power transmission device 10 compares Q_Max with a threshold value stored in the memory 24, and determines whether Q_Max is lower than the threshold value (step S30).

  If Q_Max is lower than the threshold value in the determination process in step S30, the determination unit 23B determines that there is a metal foreign object (step S5 in FIG. 17), and performs an end process. On the other hand, when Q_Max is not lower than the threshold value, the determination unit 23B determines that there is no metal foreign object (step S5 in FIG. 17), and proceeds to step S6.

  For example, when the measurement result that there is a change amount of the Q value of at least 25% between when there is no foreign metal and when there is a foreign object is a value obtained by subtracting 25% from the Q value when there is a foreign metal as an example May be used as a threshold value. Since the amount of change in the Q value varies depending on the structure and environment of the power receiving apparatus, the size and type of the metal foreign object to be detected, and the like, it is desirable to set this threshold appropriately according to the measurement target.

[Example of Q value calculation after the first time on the primary side]
Next, a process when the Q value calculation (the process of step S3) for the second and subsequent times is performed on the primary side will be described. In this example, the case where the second Q value measurement after the frequency sweep is performed will be described, but the same applies to the third and subsequent Q value measurements.

FIG. 21 is a flowchart illustrating a process when Q value calculation is performed on the primary side (power transmission device).
The processing in steps S41 to S55 in FIG. 21 corresponds to the processing in steps S11 to S26 in FIG. 18 (excluding step S24), and the following description focuses on the differences between FIG. 18 and FIG.

  When the power transmission process is started in steps S41 and S42, the main control unit 23 of the power transmission device 10 transmits the second Q value measurement command to the power reception device 30A through the communication control unit 25 (step S43). The main control unit 47 of the power receiving device 30A receives the second Q value measurement command from the power transmission device 10 through the communication control unit 49 (step S44).

As an example, the second Q value measurement command is transmitted at the head of the second Q value measurement period 61-2 (see FIG. 19). The second Q value measurement period is divided into four periods of “charging”, “Q value measurement at frequency f ₀ ”, “charging”, and “communication to the primary side”. The main control unit 47 of the power receiving device 30A switches on / off the first switch 38, the second switch 39, and the third switches 40 to 43, 43 corresponding to these four periods.

  When receiving the second Q-value measurement command, the main control unit 47 of the power receiving device 30A turns on the first switch 38, connects the capacitor 35 to the detection circuit, and charges it. At this time, the second switch 39 is turned off, and the first regulator 36, that is, the load is disconnected from the capacitor 35 (step S45).

Subsequently, the AC power supply 50 of the power receiving device 30 </ b> A outputs a test signal (sine wave) for measurement under the control of the main control unit 47. The frequency Freq of the test signal at this time is set to the frequency f ₀ (≈resonance frequency) when the largest Q value (Q_Max) is obtained in the previous frequency sweep process (step S46).

  The main control unit 23 of the power transmission device 10 stops power transmission (carrier signal transmission) to the power reception device 30A (step S47). The waiting time from the start of power transmission in step S43 to the stop of power transmission in step S47 is equal to or longer than the time required for at least the capacitor 35 to be charged with required power (power required for Q value measurement at one frequency). It is.

  The main control unit 47 of the power receiving device 30A stops power reception when power transmission from the power transmitting device 10 is stopped (step S48).

Here, the main control unit 47 turns on the third switches 40 to 43 (step S49). Then, the main control unit 47 detects the voltage V1 ′ at the other end of the capacitor 33 ′ and records it in the memory 48, and similarly detects the voltage V2 at one end of the capacitor 33 and records it in the memory 48 (step S50). ). After acquiring the voltages V1 ′ and V2 when the frequency of the test signal is f ₀ , the main control unit 47 turns off the third switches 40 to 43 and 43 ′ (step S51).

Here, the main control unit 23 of the power transmission device 10 starts power transmission to the power receiving device 30A again (step S52). The waiting time from the stop of power transmission in step S47 to the start of power transmission in step S52 is equal to or longer than the time required to detect and record at least the voltages V1 ′ and V2. In FIG. 18, power transmission to the power receiving device 30A is resumed, and then the power transmission is stopped again after the waiting time for charging the capacitor 35 has elapsed. In this example, the measurement data when the frequency of the test signal is f ₀ is used. As long as it can be acquired, power transmission is not stopped again.

The main control unit 47 of the power receiving device 30A starts receiving power from the power transmitting device 10 in response to the restart of power transmission of the power transmitting device 10, and charges the capacitor 35 (step S53).
In FIG. 9, the test signal of the next frequency Freq (f ₂ ) is output during the waiting time for charging the capacitor 35 (see step S24), but this is not performed in this example.

When the processing for obtaining the voltages V1 ′ and V2 when the frequency of the test signal is f ₀ is completed, the main control unit 47 of the power receiving device 30A turns off the first switch 38 and disconnects the capacitor 35 from the detection circuit (step S40). S54). Subsequently, the main control unit 47 of the power receiving device 30A controls the AC power supply 50 to stop the output of the test signal (step S55).

Then, the main control unit 47 of the power receiving device 30A makes a response to the second Q value measurement command from the power transmitting device 10. As a response, the threshold value used for the determination of the metallic foreign matter stored in the memory 48 and the measurement data group (f ₀ , V 1 ′, V 2) when the frequency of the test signal is f ₀ are transmitted through the communication control unit 49. 10 is returned (step S56).

The power transmitting apparatus 10 receives the threshold value and the measurement data group (f ₀ , V1 ′, V2) from the power receiving apparatus 30A and stores them in the memory 24 (step S57).

Then, the arithmetic processing unit 23A of the power transmission device 10, based on equation (1), the voltage obtained when the test signal of the frequency _{f 0} received from the power receiving device 30A V1 ', 2 primary side Q value than V2 Is calculated (step S58).

  Next, the determination unit 23B of the power transmission device 10 compares the calculated secondary Q value with the frequency sweep Q_Max stored in the memory 24, and determines whether the Q value is within a predetermined range of Q_Max. Determine. As a specific example, it is determined whether or not the Q value is X% lower than Q_Max (step S59). That is, metal foreign matter is detected using Q_Max at the previous frequency sweep as the standard Q value.

  In the determination process of step S59, if the Q value is lower than Q_Max by X% or more, the determination unit 23B determines that there is a possibility of a metal foreign object (step S4 in FIG. 17), and proceeds to step S2. On the other hand, when the Q value is not X% lower than Q_Max, the determination unit 23B determines that there is no metal foreign object (step S4 in FIG. 17), and proceeds to step S6.

In the above determination process, when the Q value is lower than the Q_Max by X% or more, the reason for determining that there is a “possibility” of the foreign metal is the positional relationship between the primary side coil and the secondary side coil as described above. This is because there is a possibility of a frequency shift due to the change of. That is, in the second Q value measurement, there is a possibility that the resonance frequency f ₀ obtained by the first Q value measurement (frequency sweep) is shifted. Therefore, the Q value (Q_Max) at the resonance frequency f ₀ obtained by the first Q value measurement (frequency sweep) and the second Q value measurement using the resonance frequency f ₀ have a large Q value. It can be different.
Therefore, if the Q value is lower by X% or more than Q_Max in the second Q value measurement, it is determined that there is a “possibility” of the metal foreign matter, and the process moves to step S2 and the frequency sweep process is performed again. Judgment of metal foreign objects is performed.

[Modification]
(Example of Q value calculation on the secondary side)
In the example of FIGS. 18 and 21, the threshold value used for the determination of the metallic foreign object, and the measurement data group (f ₀ , V 1 ′, V 2) when the frequency of the test signal is f ₀ are received by the power receiving device 30A (secondary side). To the power transmission device (primary side) 10. And in the power transmission apparatus 10, the Q value is calculated from the voltages V1 ′ and V2 of the measurement data group, and the metal foreign object is determined by comparing the Q value with a threshold value.
However, the power receiving device 30A measures the Q value from the measurement data group (f ₀ , V1 ′, V2) when the frequency of the test signal is f ₀ , and compares the Q value with the threshold value to determine the metal foreign object. You may do it. That is, only the determination result of the metallic foreign object is transmitted from the power receiving device 30 </ b> A to the power transmitting device 10.

As shown in FIG. 18, when the power transmission device 10 (primary side) calculates the Q value and determines the metal foreign object, the power receiving device 30 </ b> A (secondary side) has hardware of an arithmetic processing unit and a determination unit. There is an advantage that it is not necessary. For example, the portable device used as the power receiving device 30A can be expected to be reduced in size, weight, and cost.
On the other hand, when the power receiving device 30A calculates the Q value and determines the metal foreign object, the power receiving device 30A needs to have hardware of an arithmetic processing unit and a determination unit. However, since the information of the determination result that there is a metal foreign object or no metal foreign object is only sent to the power transmission device 10, the amount of information is small, and a reduction in communication time can be expected.

<2. Second Embodiment>
FIG. 22 shows the main part of the internal configuration example of the power transmission device (primary side) that switches the configuration (constant) of the resonance circuit according to the second embodiment example of the present disclosure at the time of power feeding and Q factor measurement. FIG.

In the power transmission device 10A according to the present embodiment, the same configuration as the resonance circuit of the power reception device 30A (see FIG. 6) is applied to the power transmission device 10 illustrated in FIG. That is, the capacitors 72, 72 ′, 73, and 73 ′ that configure the resonance circuit of the power transmission device 10A correspond to the capacitors 32, 32 ′, 33, and 33 ′ that configure the resonance circuit of the power reception device 30A.
The resonance circuit is connected to the third switches 40 to 43, 43 'used in the power receiving device 30A, and the third switches 40 to 42 are connected to the Q value measurement circuit 20'.

  The Q value measurement circuit 20 ′ is provided with an AC power supply (oscillation circuit), a resistance element, and an amplifier (all not shown) as shown in FIG. 6 with respect to the Q value measurement circuit 20. Then, an AC signal (sine wave) is supplied to one end of the capacitor 73. The third switches 41 and 42 are connected to the rectifying units 21A and 21B of the Q value measuring circuit 20 ′, respectively.

  The Q value measurement circuit 20 ′ (main control unit 23) controls the on / off of the third switches 40 to 43, 43 ′, thereby switching the configuration of the resonance circuit between power supply and Q value measurement. The voltage V1 ′ and the voltage V2 at the time of non-power feeding are measured by the Q value measuring circuit 20 ′.

  The signal source 11 outputs a control signal for controlling the generation of an AC signal, and a power transmission driver 22 that generates and outputs an AC signal having an arbitrary frequency based on the control signal of the power transmission control unit 21. Is provided. The power transmission control unit 21 and the power transmission driver 22 output an AC signal to the outside through the primary side coil 71 of the resonance circuit at least at a timing not at the time of Q value measurement.

  In addition, when operating the 3rd switch and Q detection measuring circuit which were provided in the power transmission apparatus, the power supply can use the alternating current signal which the signal source 11 outputs, the electric power stored in the battery which is not illustrated with which the power transmission apparatus is equipped, etc. .

FIG. 23 is an equivalent circuit diagram illustrating a configuration of a resonance circuit when the third switch of the power transmission device 10A is turned on and off.
In this embodiment, the third switch is turned off during power feeding, and a resonance circuit is configured by the primary coil 71 and the capacitors 72 and 73 (upper part of FIG. 23).
On the other hand, when measuring the Q value, the third switch is turned on, and a capacitor 72 ′ is further connected in parallel to the capacitor 72 in parallel with the primary coil 71, and the capacitor 73 in series with the primary coil 71 is connected. Further, a capacitor 73 'is connected in series (the bottom of FIG. 23).

Assuming that the above-described 8-turn coil was used as the primary coil 71, the constants of the resonance circuit were calculated when the third switches 40 to 43, 43 ′ were on and off.
When the third switches 40 to 43, 43 ′ were off, the resonance frequency of the resonance circuit was 121.6 kHz, the impedance of the resonance circuit at the resonance point was 0.7Ω, and the Q value was 50. The various conditions used for the trial calculation were as follows: the amplitude of the AC voltage was 0.1 V, the self-inductance of the primary coil 71 of the resonance circuit was 14.3 μH, the resistance value of the effective resistance component r1 was 0.6Ω, and the capacitors 72 and 73 Capacitance values are 10 nF and 110 nF, respectively.

On the other hand, when the third switches 40 to 43, 43 ′ were on, the resonance frequency of the resonance circuit was 227.5 kHz, the impedance of the resonance circuit at the resonance point was 8.3Ω, and the Q value was 82.
Capacitance values of the capacitors 72 'and 73' are 15 nF and 10 nF, respectively, and other conditions are the same as above.

In the present embodiment, similarly to the first embodiment, a measurement signal (sine wave signal) output from the secondary AC power source used for Q value measurement by appropriately switching the third switches 40 to 43 and 43 ′. ) And the power feeding signal fed from the primary side can be prevented from interfering with each other, and a highly accurate Q value can be calculated.
In addition, the configuration of the resonance circuit at the time of power feeding and the configuration of the resonance circuit at the time of metal foreign object detection by Q-factor measurement are each optimized (constant: capacitance value), thereby deteriorating the power feeding performance. Therefore, it is possible to improve the detection accuracy of the metallic foreign matter.
Further, similarly to the first embodiment, the present invention is not limited to the magnetic field resonance method, and can be applied to an electromagnetic induction method in which the coupling coefficient k is increased and the Q value is kept low.

  Also in this embodiment, the connection form of the capacitor to the coil of the resonance circuit is (1) series connection to the coil, (2) parallel connection to the coil, and then serial connection, and (3) parallel to the coil. Applicable to any case of connection.

  In the examples of FIGS. 16, 22, and 23, the resonance frequency of the resonance circuit is increased and the impedance is increased by switching the circuit configuration of the resonance circuit. On the other hand, as shown in FIGS. 9 to 12, only the impedance of the resonance circuit may be changed without changing the resonance frequency of the resonance circuit.

Further, in the examples of FIGS. 16, 22, and 23, the case where the capacitance of the capacitor that configures the resonance circuit is changed has been described, but the self-inductance of the coil that configures the resonance circuit may be changed.
In that case, for example, a coil with a tap is applied to the coil, and under the control of the main control unit 23, the tap is switched between power supply and Q value measurement by the circuit switching unit, and the coil that substantially constitutes the resonance circuit is changed. By changing, the self-inductance of the coil of the resonance circuit is changed. Or it is good also as a structure which switches the coil itself to another coil.

<3. Other>
(First example)
In the first and second embodiments described above, the Q value measurement circuit 60 (arithmetic processing unit 47A) and the Q value measurement circuit 20 ′ (arithmetic processing unit 23A) are connected to the voltage V1 ′ between the coil and the capacitor of the resonance circuit. The Q value is obtained from the voltage V2 across the coil. In this embodiment, the Q value is obtained by the half-value width method.

In the half width method, when a series resonance circuit is configured, a band (frequency f1 to f2) having an impedance √2 times the absolute value of the impedance (Zpeak) at the resonance frequency f0 as shown in the graph of FIG. ) From the following equation (9).

  In the case of configuring a parallel resonant circuit, as shown in the graph of FIG. 25, a band (frequency f1 to f2) in which the impedance is 1 / √2 times the absolute value of the impedance (Zpeak) at the resonant frequency f0. From Equation (9),

(Second example)
Unlike the first and second embodiments, the present embodiment is an example in which the arithmetic processing units 47A and 23A calculate the Q value from the ratio of the real part component and the imaginary part component of the impedance of the resonance circuit. In this example, the real part component and the imaginary part component of the impedance are obtained using an automatic balanced bridge circuit and a vector ratio detector.

FIG. 26 is a circuit diagram of an automatic balancing bridge circuit for calculating the Q value from the ratio of the real part component and the imaginary part component of the impedance.
The automatic balancing bridge circuit 90 shown in FIG. 26 has the same configuration as a generally well-known inverting amplifier circuit. The coil 92 is connected to the inverting input terminal (−) of the inverting amplifier 93, and the non-inverting input terminal (+) is connected to the ground. The feedback resistance element 94 applies negative feedback from the output terminal of the inverting amplifier 93 to the inverting input terminal (−). Further, the output (voltage V 1 ′) of the AC power supply 91 for inputting an AC signal to the coil 92 and the output (voltage V 2) of the inverting amplifier 93 are input to the vector ratio detector 95. The coil 92 corresponds to the secondary coil 31 of FIG. 16 or the primary coil 71 of FIG.

  The automatic balancing bridge circuit 90 operates so that the voltage of the inverting input terminal (−) is always zero by the action of negative feedback. Further, almost all of the current flowing from the AC power supply 91 to the coil 92 flows into the feedback resistance element 94 because the input impedance of the inverting amplifier 93 is large. As a result, the voltage applied to the coil 92 becomes the same as the voltage V1 ′ of the AC power supply 91, and the output voltage of the inverting amplifier 93 is the product of the current I flowing through the coil 92 and the feedback resistance value Rs. This feedback resistance value Rs is a known reference resistance value. Therefore, the impedance can be obtained by detecting the voltage V1 ′ and the voltage V2 and taking the ratio. The vector ratio detector 95 uses the phase information (one-dot chain line) of the AC power supply 91 in order to obtain the voltage V1 ′ and the voltage V2 as complex numbers.

In this example, the real component R _L of the impedance Z _L of the resonance circuit by using a such an automatic balancing bridge circuit 90 and a vector ratio detector 95 _obtains the imaginary component X _L, determine the Q value from the ratio . The following formulas (10) and (11) are calculation formulas representing the process of obtaining the Q value.

  The first to second embodiments have been described assuming a magnetic resonance type non-contact power transmission system. However, as described above, the present disclosure is not limited to the magnetic field resonance method, and can also be applied to an electromagnetic induction method in which the coupling coefficient k is increased and the Q value is kept low.

  Further, the power receiving device may have a power transmission unit, and may transmit power to the power transmission device in a non-contact manner via the secondary coil, or the power transmission device may include a load, and from the power receiving device via the power transmission coil. You may make it receive supply of electric power non-contactingly.

  In the first embodiment, the Q value measurement is performed by using the small power charged in the capacitor 35 of the power receiving device 30A. However, if the configuration of the resonance circuit is switched between the power supply time and the Q value measurement time. Since it is good, it is good also as a structure which measures Q value using the electric power of a battery. In this case, the capacitor 35 is not necessary.

  In the first to second embodiments, the Q value at the resonance frequency is measured, but the frequency at which the Q value is measured does not necessarily match the resonance frequency. Even when the Q value is measured using a frequency that deviates from an allowable range from the resonance frequency, the detection accuracy of the metallic foreign object existing between the power transmission side and the power reception side is improved by using the technique of the present disclosure. It is possible.

  In addition, when a conductor such as metal approaches the primary side coil or the secondary side coil, not only the Q value but also the L value changes and the resonance frequency shifts, but the resonance frequency of the L value changes. The shift amount and the Q value may be used together to detect the electromagnetic coupling state.

  The coupling coefficient k value also changes when a metal foreign object is sandwiched between the primary side coil and the secondary side coil. However, in order to detect the electromagnetic coupling state, the coupling coefficient k value and the Q value Changes may be used in combination.

  Moreover, although the example of the coil which does not have a core as a primary side coil and a secondary side coil was demonstrated in the 1st-2nd embodiment example of this indication, it was wound around the core with a magnetic body. A coil having a different structure may be adopted.

  Furthermore, in the first to second exemplary embodiments of the present disclosure, the example in which the mobile phone is applied to the mobile device on the secondary side has been described. However, the present invention is not limited to this example, and the mobile music player, digital still It can be applied to various portable devices that require power, such as cameras.

In addition, this indication can also take the following structures.
(1)
A resonant circuit including at least a coil and a capacitor;
A detector for measuring the Q value of the resonant circuit;
A circuit switching unit that switches a circuit configuration of the resonance circuit between power supply and Q value measurement;
A control unit that controls switching by the circuit switching unit.
(2)
The detection unit according to (1), wherein the detection unit detects an electromagnetic coupling state between the coil and the outside by measuring a Q value of the resonance circuit.
(3)
The detection device according to (2), wherein the circuit switching unit switches a circuit configuration of the resonance circuit between power supply and Q value measurement, and changes a resonance frequency of the resonance circuit.
(4)
The circuit switching unit switches the circuit configuration of the resonance circuit between power supply and Q-factor measurement, changes the resonance frequency of the resonance circuit, and increases the impedance at the resonance frequency of the resonance circuit (2) The detection device according to (3).
(5)
The detection device according to any one of (2) to (4), wherein the circuit switching unit switches a circuit configuration of the resonance circuit between power feeding and Q value measurement, and increases impedance at a resonance frequency of the resonance circuit.
(6)
The detection device according to any one of (3) to (5), wherein the circuit switching unit changes a capacitance value of a capacitance component of the resonance circuit when measuring a Q value.
(7)
The detection device according to any one of (3) to (6), wherein the circuit switching unit changes a capacitance value of a capacitance component in parallel and in series with the coil of the resonance circuit when measuring a Q value.
(8)
The detection device according to any one of (3) to (6), wherein the circuit switching unit changes a capacitance value of a capacitance component in parallel with the coil of the resonance circuit when measuring a Q value.
(9)
The detection device according to any one of (3) to (6), wherein the circuit switching unit changes a capacitance value of a capacitance component in series with the coil of the resonance circuit when measuring a Q value.
(10)
The detection device according to any one of (7) and (8), wherein the circuit switching unit increases a capacitance value of a capacitance component in parallel with the coil during Q value measurement.
(11)
The detection device according to (7) or (9), wherein the circuit switching unit decreases a capacitance value of a capacitance component in series with the coil at the time of Q value measurement.
(12)
The said circuit switching part switches the self-inductance of the said coil of the said resonance circuit at the time of Q value measurement. The detection apparatus as described in said (3)-(11).
(13)
The coil is a tapped coil;
The detection device according to (12), wherein the circuit switching unit switches a tap of the tapped coil.
(14)
The detection device according to any one of (1) to (13), wherein the resonance circuit has a configuration in which a capacitor is connected in series to the coil.
(15)
The detection device according to any one of (1) to (13), wherein the resonance circuit has a configuration in which a capacitor is connected in parallel to the coil.
(16)
The detection device according to any one of (1) to (13), wherein the resonance circuit has a configuration in which one capacitor is connected in parallel to the coil and another capacitor is connected in series.
(17)
A coil for receiving power;
A resonant circuit including at least the coil and the capacitor;
A detector for measuring the Q value of the resonant circuit;
A circuit switching unit that switches a circuit configuration of the resonance circuit between power supply and Q value measurement;
And a control unit that controls switching by the circuit switching unit.
(18)
A coil for transmitting power;
A resonant circuit including at least the coil and the capacitor;
A detector for measuring the Q value of the resonant circuit;
A circuit switching unit that switches a circuit configuration of the resonance circuit between power supply and Q value measurement;
A control unit that controls switching by the circuit switching unit.
(19)
A power transmission device that wirelessly transmits power, and a power reception device that receives power from the power transmission device,
Either the power transmission device or the power reception device is:
A resonant circuit including at least a coil and a capacitor used for power transmission or power reception;
A detector for measuring the Q value of the resonant circuit;
A circuit switching unit that switches a circuit configuration of the resonance circuit between power supply and Q value measurement;
A non-contact power transmission system comprising: a control unit that controls switching by the circuit switching unit.
(20)
For a resonance circuit including at least a coil and a capacitor included in a power transmission device or a power reception device constituting the non-contact power transmission system, at the time of Q value measurement, the circuit configuration of the resonance circuit is switched from the circuit configuration at the time of power supply,
Measuring the Q value of the resonant circuit after switching the circuit configuration of the resonant circuit;
Detection method including.

  The series of processes in the above-described embodiment can be executed by hardware, but can also be executed by software. When a series of processing is executed by software, it can be executed by a computer in which a program constituting the software is incorporated in dedicated hardware or a computer in which programs for executing various functions are installed. is there. For example, what is necessary is just to install and run the program which comprises desired software in a general purpose personal computer.

  Further, a recording medium on which a program code of software that realizes the functions of the above-described embodiments may be supplied to the system or apparatus. It goes without saying that the function is also realized by a computer (or a control device such as a CPU) of the system or apparatus reading and executing the program code stored in the recording medium.

  As a recording medium for supplying the program code in this case, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like is used. Can do.

  Further, the functions of the above-described embodiment are realized by executing the program code read by the computer. In addition, based on the instruction of the program code, the OS running on the computer performs part or all of the actual processing. The case where the functions of the above-described embodiment are realized by the processing is also included.

  Further, in this specification, the processing steps describing time-series processing are not limited to processing performed in time series according to the described order, but are not necessarily performed in time series, either in parallel or individually. The processing (for example, parallel processing or object processing) is also included.

As described above, the present disclosure is not limited to each of the above-described embodiments, and various other modifications and application examples can be taken without departing from the gist described in the claims. .
That is, the examples of the above-described embodiments are preferable specific examples of the present disclosure, and thus various technically preferable limitations are given. However, the technical scope of the present disclosure is not limited to these forms unless specifically described in each description to limit the present disclosure. For example, the materials used in the above description, the amount used, the processing time, the processing order, the numerical conditions of each parameter, etc. are only suitable examples, and the dimensions, shapes, and arrangement relationships in each figure used for the description are also included. Schematic.

DESCRIPTION OF SYMBOLS 10 ... Power transmission apparatus, 14 ... Capacitor, 15 ... Primary side coil, 20 ... Q value measurement circuit, 23 ... Main control part, 23A ... Arithmetic processing part, 23B ... Determination part, 24 ... Memory, 31 ... Secondary side coil , 32, 32 ', 33, 33' ... capacitor, 34 ... rectifier, 35 ... capacitor, 37 ... second regulator, 38 ... first switch, 39 ... second switch, 40-43, 43 '... third switch 45A, 45B ... envelope detection unit, 47 ... main control unit, 47A ... arithmetic processing unit, 47B ... determination unit, 48 ... memory, 60 ... Q value measuring circuit, 71 ... primary coil, 72, 72 ', 73 , 73 '... capacitor

Claims (14)

A resonant circuit including at least a coil and a capacitor;
A detector for measuring the Q value of the resonant circuit;
A control unit for supplying an AC signal for measurement to the resonance circuit in a state where transmission of power between the power supply source and the power supply destination is stopped, and controlling the Q value to be measured by the detection unit;
A determination unit that compares the measured Q value with a prescribed Q value . When the AC signal for measurement is supplied to the resonance circuit, the detection unit calculates the resonance circuit based on a ratio between a first voltage applied to the coil and the capacitor and a second voltage applied to the coil. The detection device according to claim 1, wherein a Q value of the is measured. A first analog-to-digital converter that converts an analog DC signal based on an AC signal corresponding to the first voltage into a digital first DC signal;
A second analog-to-digital converter that converts an analog DC signal based on an AC signal corresponding to the second voltage into a digital second DC signal;
The control unit includes a determination unit that determines whether or not a metal foreign object is nearby based on a Q value of the resonance circuit calculated using the first DC signal and the second DC signal. The detection device according to claim 2. The control unit uses the first DC signal and the second DC signal output from each of the first analog-digital converter and the second analog-digital converter to generate the resonance circuit. The detection device according to claim 3, further comprising: an arithmetic processing unit that calculates a Q value of. The detection device is provided on the primary side that is the power supply source,
The determination unit acquires a value for Q value comparison from a secondary side that is a power supply destination, and compares the acquired value with a specified Q value.
The detection device according to claim 1. A storage unit for storing the prescribed Q value;
The determination unit acquires the prescribed Q value from the storage unit.
The detection device according to claim 1. The supply source of the AC signal for measurement supplied to the resonance circuit is different from the power supply source.
The detection device according to claim 1. A coil for receiving power;
A resonant circuit including at least the coil and the capacitor;
A detector for measuring the Q value of the resonant circuit;
A control unit for supplying an AC signal for measurement to the resonance circuit in a state where transmission of power between the power supply source and the power supply destination is stopped, and controlling the Q value to be measured by the detection unit;
A power receiving apparatus comprising: a determination unit that compares the measured Q value with a specified Q value . A coil for transmitting power;
A resonant circuit including at least the coil and the capacitor;
A detector for measuring the Q value of the resonant circuit;
A control unit for supplying an AC signal for measurement to the resonance circuit in a state where transmission of power between the power supply source and the power supply destination is stopped, and controlling the Q value to be measured by the detection unit;
And a determination unit that compares the measured Q value with a prescribed Q value . A power transmission device that wirelessly transmits power, and a power reception device that receives power from the power transmission device,
Either the power transmission device or the power reception device is:
A resonant circuit including at least a coil and a capacitor used for power transmission or power reception;
A detector that measures the Q value of the resonant circuit in a state where power transmission between the power supply source and the power supply destination is stopped ;
A control unit for controlling the Q value to be measured by the detection unit by supplying an AC signal for measurement to the resonance circuit when not fed;
A non-contact power transmission system comprising: a determination unit that compares the measured Q value with a specified Q value . Either the power transmission device or the power reception device further includes a memory that stores a threshold value of a Q value of the resonance circuit,
The control unit compares the Q value of the resonance circuit measured by the detection unit with the threshold value of the Q value of the resonance circuit stored in the memory, and based on the comparison result, a metallic foreign object is near. The non-contact power transmission system according to claim 10 . Either the power transmission device or the power reception device is:
A first rectifier that converts an analog AC signal corresponding to a first voltage applied to the coil and the capacitor into an analog DC signal;
The non-contact power transmission system according to claim 10 , further comprising: a second rectification unit that converts an analog AC signal corresponding to the second voltage applied to the coil into an analog DC signal. The contactless power transmission system according to claim 10 , wherein either the power transmission device or the power reception device further includes an input unit that generates an input signal corresponding to a user operation and outputs the input signal to the control unit. . When the Q value is measured in a state where power transmission is stopped between a power supply source and a power supply destination for a resonance circuit including at least a coil and a capacitor included in the power transmission device or power reception device constituting the non-contact power transmission system, the resonance occurs. Supplying an AC signal for measurement to the circuit;
Measuring a Q value of the resonance circuit the AC signal is supplied for the measurement,
Comparing the measured Q value with a specified Q value;
Detection method including.

Images